Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-02-26
2001-05-08
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C420S560000, C420S561000, C420S562000
Reexamination Certificate
active
06229248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a solder alloy suitable for bonding a terminal etc., for example, in an inside of an electronic component, and, more particularly, relates to a solder alloy having excellent thermal shock resistance.
2. Related Art of the Invention
Conventionally, a structure which contains a piezoelectric resonator in a package which does not obstruct oscillation of a piezoelectric resonator has been widely used in piezoelectric resonance components, etc. In these types of piezoelectric resonance components, the piezoelectric resonator and an electrode and a terminal, etc. which are disposed on the package are bonded with solder.
In the solder for bonding to the inside of an electronic component, i.e., a so-called internal solder, heat stress resistance at the time of the soldering for mounting an electronic component in a printed circuit board etc. is required. Therefore, it is strongly required that the internal solder be difficult to melt by heat stress at the time of mounting electronic-component and be characterized by being difficult to cause cracks, etc.
Conventionally, an eutectic solder of Sn—Pb with a comparatively high melting point and Sn—Sb eutectic solder are used as the internal solder to withstand the heat stress in mounting the electronic components.
When prevention of diffusion of solder to the electrode surface is required, a Pb-rich composition eutectic solder such as an eutectic solder of the composition which includes 60 wt % of Sn and 40 wt % of Pb is used.
When a prevention of solder diffusion such as by forming Ni barrier phase on an electrode surface is desired, a Sn-rich solder such as Sn—Sb system eutectic solder is used.
However, the above described internal solders have a problem in that the thermal shock resistance is not sufficient.
In Sn—Pb system eutectic solder, a Pb-rich phase (alpha-phase) and a Sn-rich phase (beta-phase) grow. However, there is the problem that a correlation crack is produced between the alpha-phase and the beta-phase or that a crack in the alpha-phase is produced.
In Sn—Sb system solder which does not contain Pb, such as the above Sn—Sb system solder, the above described cracks are hardly caused. However, the Sn—Sb system solder has a high Young's modulus. Therefore, when a heat stress is imposed, the solder easily mechanically damages the electrodes, and easily causes electrode peeling, etc.
SUMMARY OF THE INVENTION
To overcome the above described problems, preferred embodiments of the present invention provide a solder alloy having an excellent thermal shock resistance. When a heat stress is imposed, it is difficult to cause a crack. Also, it is hard to mechanically damage bonded electrodes.
One preferred embodiment of the present invention provides a solder alloy comprising a metal alloy of Sn, Sb, Ag and Cu, wherein: the amount of the Sb is about 1.0-3.0 wt %; the amount of the Ag is about 1.0 wt % or more and about 2.0 wt % or less; the amount of the Cu is about 1.0 wt % or less; and the remainder is Sn.
The above described solder alloy has a comparatively low Young's modulus and sufficient tensile characteristics. Therefore, it is hard to cause peeling from the bonded electrode, etc., even though a heat stress is present. Also, a solder which has an excellent solderbility to metal phases such as Cu and Ni can be provided. Therefore, a solder alloy excellent in thermal shock resistance can be provided.
The above described solder alloy may be used for soldering the inside of an electronic component.
When using the above described solder alloy as internal solder of an electronic component, even though the heat stress is present at the time of the soldering in mounting the electronic component on a printed circuit board, etc., re-melting and electrode peeling hardly occur and cracks in the bonded internal solder can also be prevented reliably.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 5352407 (1994-10-01), Seelig et al.
patent: 5-50286 (1993-03-01), None
Kusabiraki Shigemasa
Sumita Manabu
Dougherty Thomas M.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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